病原体の伝播

Pathogens spread from a reservoir, such as an infected individual, to susceptible hosts through three main routes: contact transmission, vehicle transmission, and vector transmission.

Direct contact transmission, such as a handshake, can spread pathogens like Streptococcus pyogenes.

Indirect transmission happens through contaminated objects or surfaces, called fomites.

Droplet transmission happens when infected respiratory droplets are expelled during coughing or sneezing, spreading infection over short distances.

Airborne vehicle transmission involves smaller droplets that remain suspended in the air, spreading pathogens over long distances without close contact.

Pathogens can also spread via waterborne vehicle transmission, where consuming contaminated water causes illnesses like cholera.

In mechanical vector transmission, a vector, such as a fly, passively carries pathogens on its body and transfers them to a host.

In biological vector transmission, the pathogen multiplies within the vector. For example, Plasmodium develops inside mosquitoes before being transmitted to humans.